First, you need a way to keep Mars warm. The Earth's atmosphere is not a warm enough blanket for Mars because it gets only half the amount of sunlight as Earth.
Assuming that the aliens have fixed that - with alien tech it could be for instance by orbiting thin film mirrors the size of a planet reflecting extra sunlight on Mars to keep it warm. And assume they've made this so it will work flawlessly.
Then next problem is that it may lose its carbon dioxide. Doesn't need much. Fraction of a percent like Earth. But on Mars with no continental drift, it would all get lost into the oceans as carbonates. No volcanoes producing CO2 to return it to the atmosphere.
Supposing that the Aliens have thought of this too, and seeded it with something that returns the CO2 to the atmosphere - maybe a lifeform that dissolves carbonate rocks with acid, say.
So next problem is that over long timescales it will lose its atmosphere and return to its present state. To fix that they have to give it a magnetic field somehow or have magnetic field generators in space or on the surface.
The other long term problem is - what about the lifeforms there themselves? On Earth we have a finely balanced global ecosystem where all the lifeforms work together. Does it work also on Mars?
So - again that requires far seeing ETs that have an intimate knowledge of ecosystems and able to set one up that will work in the rather different conditions of Mars. Apart from anything else, Mars has a third of the gravity of Earth which surely has some effect on how things grow. But it also means you need to produce three times as much oxygen, for instance, to maintain the same partial pressure of oxygen in the atmosphere. And we already had to add these carbonate rock decomposing lifeforms to get it to work (unless somehow they can give Mars continental drift).
There are other cycles also that would have to work perfectly on Mars, e.g. nitrogen.
I think that if any Alien did this, it would involve a very impressive level of understanding of life, evolution, exoplanets, ecosystems etc. With a millions of years old civilization they have probably done this thousands of times before and know it works. So then hard to put any limits on what they can and can't do. But at least with current understanding it would seem to involve a fair bit of mega technology. And surely an understanding way ahead of ours.
Mars may also become habitable briefly in the far future of the solar system as the sun gets hotter, just by itself, without any aliens to do it. Depends though on what "habitable" means by then - no guarantee that the intelligent lifeforms on Earth by then are oxygen breathing land dwellers, never mind primates. Far enough in the future for humans to evolve a second time all the way from creatures that you need a microscope again.
Assuming that the aliens have fixed that - with alien tech it could be for instance by orbiting thin film mirrors the size of a planet reflecting extra sunlight on Mars to keep it warm. And assume they've made this so it will work flawlessly.
Then next problem is that it may lose its carbon dioxide. Doesn't need much. Fraction of a percent like Earth. But on Mars with no continental drift, it would all get lost into the oceans as carbonates. No volcanoes producing CO2 to return it to the atmosphere.
Supposing that the Aliens have thought of this too, and seeded it with something that returns the CO2 to the atmosphere - maybe a lifeform that dissolves carbonate rocks with acid, say.
So next problem is that over long timescales it will lose its atmosphere and return to its present state. To fix that they have to give it a magnetic field somehow or have magnetic field generators in space or on the surface.
The other long term problem is - what about the lifeforms there themselves? On Earth we have a finely balanced global ecosystem where all the lifeforms work together. Does it work also on Mars?
So - again that requires far seeing ETs that have an intimate knowledge of ecosystems and able to set one up that will work in the rather different conditions of Mars. Apart from anything else, Mars has a third of the gravity of Earth which surely has some effect on how things grow. But it also means you need to produce three times as much oxygen, for instance, to maintain the same partial pressure of oxygen in the atmosphere. And we already had to add these carbonate rock decomposing lifeforms to get it to work (unless somehow they can give Mars continental drift).
There are other cycles also that would have to work perfectly on Mars, e.g. nitrogen.
I think that if any Alien did this, it would involve a very impressive level of understanding of life, evolution, exoplanets, ecosystems etc. With a millions of years old civilization they have probably done this thousands of times before and know it works. So then hard to put any limits on what they can and can't do. But at least with current understanding it would seem to involve a fair bit of mega technology. And surely an understanding way ahead of ours.
Mars may also become habitable briefly in the far future of the solar system as the sun gets hotter, just by itself, without any aliens to do it. Depends though on what "habitable" means by then - no guarantee that the intelligent lifeforms on Earth by then are oxygen breathing land dwellers, never mind primates. Far enough in the future for humans to evolve a second time all the way from creatures that you need a microscope again.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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